An example of an airship built on the same principle as the Zeppelins was the first American-built rigid dirigible ZR-1 USS Shenandoah, which flew in 1923, while USS Los Angeles (ZR-3) was under construction. The ship was christened on 20 August in Lakehurst, New Jersey and was the first to be inflated with helium, which was still so rare at the time that Shenandoah contained most of the world's reserves. When Los Angeles was delivered, she was at first filled with helium borrowed from ZR-1. Other airships were the USS Akron (ZRS-4) and the USS Macon (ZRS-5).